Low Temperature Processing of Dielectric Thin Films Chris Bratten Advisors Prof. E. Slamovich Prof. H. Hillhouse Chris Bratten Advisors Prof. E. Slamovich Prof. H. Hillhouse

Research Goals Produce thin films of Barium Titanate using hydrothermal synthesis Produce thin films of Barium Titanate using hydrothermal synthesis Verify formation of BaTiO 3 on substrates using x-ray diffraction Verify formation of BaTiO 3 on substrates using x-ray diffraction Determine the dielectric properties of the films produced Determine the dielectric properties of the films produced

ProcessProcess Used ½ length glass slides as substrates Used ½ length glass slides as substrates Cleaned slides using TCA, acetone and methanol Cleaned slides using TCA, acetone and methanol Sputtered 2 platinum electrodes Sputtered 2 platinum electrodes Deposited a thin film of titanium onto the slides by evaporation to connect the 2 Pt electrodes Deposited a thin film of titanium onto the slides by evaporation to connect the 2 Pt electrodes

Process (cont) Samples immersed in solution Samples immersed in solution – 125mL PE bottle – 1M BaCl 2 + NaOH – 1M Ba(OH) 2 “Baked” at temperatures between 60 and 90 o C for about 24 hours or more “Baked” at temperatures between 60 and 90 o C for about 24 hours or more

Process (cont) Samples removed from solution in a nitrogen atmosphere (glove box) Samples removed from solution in a nitrogen atmosphere (glove box) Avoid formation of barium carbonate Avoid formation of barium carbonate Rinsed in a ph=12 solution then placed in ethanol Rinsed in a ph=12 solution then placed in ethanol – Solutions kept warm in oven – Samples taken out of glove box while immersed in ethanol Samples removed from ethanol and blown dry with air Samples removed from ethanol and blown dry with air

Initial Results

…Later on… Changes Changes

ProblemsProblems Film adhesion Film adhesion – Platinum being stripped from slide in solution – Same for titanium, but not as much over platinum Barium Carbonate Barium Carbonate – Contaminant – Result of reaction with carbon dioxide in air or solution

ChangesChanges Switched solution Switched solution – 1M Ba(OH) 2 – Better results, visually – Still had film loss in solution, but not as much as before Stopped depositing platinum Stopped depositing platinum – Mostly lost in solution – Getting rid of an extra step

ResultsResults

Capacitance Testing Tested the 3 best samples based on XRD information Tested the 3 best samples based on XRD information Used TEM grids as a mask and deposited titanium over the sample Used TEM grids as a mask and deposited titanium over the sample Created a grid of electrodes Created a grid of electrodes Used a LCR meter and probes to test capacitance of film between electrodes Used a LCR meter and probes to test capacitance of film between electrodes

Capacitance Testing

Capacitance and Temperature

Dielectrics and Temperature

ConclusionsConclusions Film qualities with relation to temperature Film qualities with relation to temperature – Based on XRD data: Higher Temperatures lead to more BaTiO 3 Higher Temperatures lead to more BaTiO 3 – Based on LCR data: Too close to call Too close to call – Generally, a higher temperature will produce a better film Fresh solutions lead to better films Fresh solutions lead to better films Solutions “baked” for more than 24 hours showed no major advantage over others Solutions “baked” for more than 24 hours showed no major advantage over others

Thanks To… Prof. Slamovich Prof. Hilhouse MSEE Department Purdue University My Fellow REU Students